Predation on mud crab megalopae, Panopeus herbstii H Milne Edwards: Effect of habitat complexity, predator species and postlarval densities

Laboratory experiments were conducted to evaluate the magnitude of predation on megalopae of the Atlantic mud crab, Panopeus herbstii H. Milne Edwards, in four simulated habitats (salt marsh bottom, shell bottom, seaweed patch and sand bottom). Predators included juvenile blue crabs (Callinectes sapidus Rathbun), common killifish (Fundulus heteroclitus (L.)) and grass shrimp (Paleomonetes pugio Holthius). Experiments were run at two different densities of megalopae. Two-way analysis of variance revealed significant effects of predator type and substratum. Proportional mortality was lowest on shell bottom, and blue crabs were the least effective predators, regardless of habitat. Additionally, proportional mortality was lower at low megalopal densities than at high megalopal densities. Decreased predation at low megalopal abundance may afford density-dependent modulation of mud crab populations.